A Liberian man is being tested for the deadly Ebola virus after he collapsed on arrival at an airport in Nigeria's commercial capital, Lagos, a megacity of 21 million people, the Lagos State Health Ministry said on Thursday.

Ebola has killed 660 people across Guinea, Liberia and Sierra Leone since it was first diagnosed in the region in February.

If confirmed, the case would be the first on record of one of the world's deadliest diseases in Nigeria, Africa's biggest economy and, with 170 million people, its most populous country.

The special adviser on public health to the Lagos state government, Yewande Adeshina, told a news conference that the man, who is in his 40s, arrived at Lagos airport from Liberia on Sunday. He was rushed to a hospital and put in an isolation ward, she said.

"The patient was admitted and detained on suspicion of possible EBV infection, and blood sample collection and testing was initiated," she said. The test results were pending, she said.

A spokesman for the World Health Organization in Geneva confirmed one suspected case of Ebola in Nigeria and said samples had been sent to a WHO lab for testing.

Adeshina said Lagos state authorities requested the flight's manifest to contact the other passengers. They also wanted to trace the man's travel route and had already distributed protective clothing to health workers, she said.

Ben Neuman, a virologist and Ebola expert at Britain's University of Reading, said it was important to note that Ebola is one of a number of viruses that can cause hemorrhagic fever, and that others, including Lassa fever virus and Dengue virus, could turn out to be the diagnosis in this case.

"Some of these other, more common, hemorrhagic fever viruses have already been the cause of false alarms in the ongoing western African Ebola outbreak," Neuman told Reuters in London, urging calm.

Health workers at risk

Nigeria has some of the continent's weakest healthcare infrastructure, despite access to billions of dollars of oil money as Africa's biggest producer of crude oil.

The Ebola outbreak started in Guinea's remote southeast and has since spread, aided by a lack of information about the disease.

A recent wave of infections among medical personnel is raising questions about the preparedness of regional health structures.

Sierra Leone announced on Wednesday that Sheik Umar Khan, the doctor leading the fight against Ebola in the country, had himself contracted the disease following the deaths of several nurses at the treatment center where he works.

Dozens of nurses at the center staged a sit-down strike this week, calling for management of the government-run facility to be transferred to medical charity Medecins Sans Frontieres.

"If you have that number of health personnel being infected within a relatively short period of time, there is definitely something wrong with the system," Deputy Health Minister Abu Bakarr Fofanah said.

(China Daily 07/26/2014 page10)